Apparatus and method for rearing shrimp

ABSTRACT

An apparatus and method for rearing shrimp through the larvae stage wherein the shrimp are subjected to controlled conditions and a common enclosure for the male and female adult shrimp is provided which permits uncontrolled access of the shrimp to one another and wherein the shrimp are maintained through a plurality of cycles of mating, spawning and hatching. The system is further provided with filtration means for filtering the medium of the common enclosure and with collecting means for collecting hatched shrimp at preselected times from the common enclosure medium as the medium moves into the filtration means.

BACKGROUND OF THE INVENTION

This invention relates to a process and system for rearing shrimp and,in particular, to a process and system for rearing shrimp to thepost-larvae stage on a commercial scale under controlled conditions.

In recent years, there has been considerable interest in the developmentof techniques for rearing or cultivating shrimp in artificial or indoorenvironments under controlled conditions. Techniques of this type can beviewed as falling into two types of systems and processes directed tothe growing of shrimp before and after they have reached the larvaestage. The former type systems and processes primarily concern therearing stages of mating of adult shrimp, spawning of shrimp eggs by thegravid female, hatching of the spawned eggs, and the cultivation of thehatched baby shrimp to the post-larvae stage. More particularly, thesesystems and processes have attempted to control the environmentalconditions, such as, for example, lighting, temperature, and watermake-up, so as to provide conditions which promote the aforementionedrearing stages year round. However, while successful in this regard tosome degree, they have often employed cumbersome procedures requiringsignificant amounts of time. As a result, they have not proved entirelysuitable for commercial production.

For example, in these systems it is often the case that the stages ofmating, spawning, hatching and cultivating require the movement of theadult shrimp to and from various tanks, which is a time consumingprocess. Thus, females, once they are gravid, are often moved from theirmating or brood tank to a spawning tank where they drop their eggs.Likewise, the females, after spawning, are again moved from the spawningtank prior to the hatching process. Movement of the adult shrimp fromthe brood tank is also often carried out to permit drainage andsubsequent refilling of the tank.

U.S. Pat. No. 3,473,509 discloses one such controlled type process inwhich after mating and spawning, the adult shrimp are removed from thetank prior to hatching. U.S. Pat. No. 3,682,138 discloses another ofthese processes. In this case, each adult female shrimp is isolated froma male shrimp, until the female shrimp has molted and is ready to mate.At this time, the barrier between the shrimp is removed and matingoccurs. Subsequent thereto, the female is removed from the tank to afurther facility where hatching is to take place. Further patentreferences disclosing similar movement of a gravid female to a separatehatching tank are as follows: U.S. Pat. Nos. 3,685,489; 3,696,788;3,540,414. Additionally, this type of movement of a gravid female isdisclosed in C.C. Dugan, W. Hagood, Thomas A. Franks, "Development ofSpawning and Mass Larvae Rearing Techniques for Brackish-FreshwaterShrimps of the Genus Macrobrachium (Decopoda Palaemonidae), "FloridaMarine Publications, No. 12 (October 1975). The latter publicationfurther discloses a collection system for collecting the shrimp afterhatching by trapping them in collectors placed in the water flow passingfrom the hatching tank.

As can be appreciated, the above movement of the adult shrimp from onetank to another is time consuming and not entirely satisfactory wherecommercial production of shrimp is sought.

It is thus an object of the present invention to provide a process andapparatus for cultivation of shrimp to the larvae stage which is moreefficient and, hence, geared to commercial production.

In systems of the above type, once hatching has occurred, the resultantbaby shrimp are placed in so-called larvae tanks where they are keptuntil they mature through the larvae stage. The larvae tanks provided todate, however, have suffered from a variety of problems all of whichhave contributed to larvae mortality. One tank construction which hashad some degree of success includes an upper cylindrical tank portionand a lower or bottom conical tank portion. This type of constructionfacilitates suspension of the larvae and larvae food, thereby preventingthe accumulation of bottom debris. However, the sharp conical taper ofthe bottom tank portion causes pile up of larvae who descend duringmolting, thereby increasing larvae mortality.

It is, therefore, a further object of the present invention to provide amethod and apparatus for growing shrimp through the larvae stage whichis provided with an improved larvae rearing tank structure.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention, the aboveand other objectives are realized via a system for rearing shrimpthrough the larvae stage wherein the shrimp are subjected to controlledconditions and a common enclosure for the male and female adult or broodshrimp is provided which permits uncontrolled access of the shrimp toone another and wherein the brood shrimp are maintained through aplurality of cycles of mating, spawning and hatching. The system isfurther provided with filtration means for filtering the medium of thecommon enclosure and with collecting means for collecting hatched shrimpat preselected times from the common enclosure medium as it moves intothe filtration means.

In the present system, the adult brood shrimp are thus maintained in thesame enclosure throughout a number of cycles of mating, spawning andhatching, thereby eliminating the time consuming prior art procedures ofseparating gravid shrimp from the remainder of the brood stock prior tohatching and/or the procedure of separating the female shrimp afterhatching from the hatched eggs. The filtration of the enclosure,moreover, maintains the enclosure medium free from contamination, whileit simultaneously provides a gentle current which attracts the hatchedlarvae, thereby aiding the larvae in moving from the enclosure into thecollecting means. The latter, in turn, is placed in the intake of thefiltration system daily during preselected morning hours, therebyensuring capture of substantially all the hatched shrimp and preventingmortality due to cannibalsm by the adults, which would occur if thehatched shrimp were allowed to remain in the enclosure.

In a further aspect of the system of the invention, a larvae tank forrearing the hatched shrimp is provided whose configuration contributesto a lessening of shrimp mortality. This tank comprises an upperportion, preferably cylindrical, and a lower conical portion whosebottom is truncated to form a flat relatively broad bottom wall. Thedegree of truncation of this conical portion is such as to preventsignificant overcrowding of the hatched shrimp or larvae who descend tothe tank bottom during molting, thereby reducing larvae mortality. Thetank is also provided with means for daily flushing of a considerableportion of the tank medium whereby the medium is kept substantiallycontaminant free. During this procedure, the larvae are confined withinthe tank bottom, but are afforded ample room due to the truncationthereof. Means is also provided for refilling the tank through adispersive water flow this type of flow being such as not to damage thelarvae.

In still further aspects of the invention, the system is furtherprovided with Artemia hatching tanks and an Artemia collector forcollecting hatched Artemia which are used as a food supplement for thelarvae. These tanks are provided with a sharp conical bottom having apipe or conduit receiving aperture through which extends a cylindricalconduit which together with the lower portion of the conical bottom actsas a debris collector and permits collecting of the Artemiasubstantially free of debris.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and aspects of the present invention willbecome more apparent upon reading the following detailed description inconjunction with the accompanying drawings, in which:

FIG. 1 shows in schematic fashion an overall view of a system embodyingthe apparatus and method of the present invention;

FIG. 2 shows in perspective view the larvae tanks, brood tanks andfiltration tanks of FIG. 1;

FIG. 3 is a cross section taken through a larvae tank, filtration tankand brood tank of FIG. 2;

FIG. 4 shows in perspective view a collection means in the filtrationtank of FIG. 3;

FIGS. 5 and 6 show perspective and cross section views of an Artemiatank of the system of FIG. 1;

FIGS. 7-9 illustrate perspective, cross section and top views of anArtemia collector in accordance with the system of the invention; and

FIG. 10 shows in block diagram form the electrical control for lights ofthe system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows in schematic fashion an overall view of a system embodyingthe shrimp rearing apparatus and method of the present invention. Thesystem is housed within a concrete building 1 so as to aid inmaintaining the system under controlled conditions. The system comprisesa plurality of similar common enclosures or tanks 2 each of which servessimultaneously as a mating, spawning and hatching tank. These tanks arearranged in rows of adjacent columns and each is provided immediatelyadjacent one of its narrow walls with a filtration means also in theform of a tank 3.

As shown more clearly in FiG. 2. a number of larvae rearing tanks 4 aresupported in frames 5 immediately above the brood tanks 2. A furthernumber of Artemia tanks 6 are arranged in an area adjacent the tanks 2.Water is supplied to the tanks 2, 4 and 6 from delivery pipes 7 coupledto a common manifold 8. Another manifold 9 is also provided for carryingair under pressure. From this manifold air is coupled via air lines 11to air stones 12 in various tanks and to air lifts 13 in the filtrationtanks 3. (See FIG. 3).

Although not specifically shown, heaters are provided adjacent the tankarea for controlling the air temperature and for maintaining thetemperature of water in the tanks at a predetermined level. Likewise,artificial lighting 14 (see FIG. 3) whose on and off period iscontrolled, as will be discussed hereinbelow, is provided above thetanks so as to ensure a preselected lighting period.

As can be seen from FIG. 3, each of the common enclosures or tanks 2 hasa common wall 15 with its adjacent filtration tank 3. Individualhabitats 16 are provided within the enclosure 2, these habitats beingprovided for adult male and female shrimp 17 and 18 deposited therein.These habitats open into a common area 19 which is freely accessible toall the shrimp at all times.

Openings 21 in the common wall 15 receive pipe or conduit 22 fordelivering the enclosure medium 23 from the enclosure into the filtertank 3. The lower portion of the filter tank 3 is provided with abio-filter 24 comprised of coral rock 25 upon which live nitrificationbacteria. This bio-filter filters the incoming medium 23 which is thenconveyed via a conventional air-lift 13 comprising air line 11 andconduit 26 back into the enclosure. This filtration maintains medium 23substantially free of contaminants and debris and avoids having tofrequently fill and refill the large enclosure volume. Typically, thefiltration system is adjusted to maintain the following acceptablecontaminant levels in the medium 23: less than 1 ppm ammonia; less than10 ppm nitrite-nitrate; a pH of 7.0±1.0 and a dissolved oxygen levelgreater than 5 ppm. Also the medium is made slightly brackish to aid inthe prevention of disease and encourage spawning. Typically, a salinityof 3±1 ppt is acceptable.

As above noted, both the lighting and temperature of the building 1 arecontrolled so as to subject the shrimp in all the tanks to predeterminedconditions. In particular, the lighting is controlled so that light isprovided for a 14 hour period per day. This is accomplished in aconventional manner as shown in FIG. 10 by providing a standard timer101 in the electrical line 102 connecting the power source 103 to thelights 14. Typically, the timer is set so that the lights are turned onat 7 a.m. and off at 9 p.m. The temperature control, on the hand, iseffected, as above noted, through the use of conventional space heatersin the area adjacent the tanks. These heaters are set so that the shrimpare subjected to a temperature of approximately 28.5° C.

Typically, each enclosure 2 is provided with 8 adult male and 50 adultfemale shrimp. These shrimp, as above-noted, have free access to thecommon area 19 of their enclosure and due to the aforementionedartificial environmental conditions provided go through the rearingstages of mating, spawning and hatching continously year round.Tyically, under these conditions each female shrimp can be made toreproduce every 6 weeks. After mating has occurred and a female's eggsare fertilized, the gravid female is maintained in its respectiveenclosure 2 and allowed to hatch her eggs, which typically might take aneighteen day period.

Once the eggs of the female are hatched, the baby shrimp or larvae arein the same enclosure 2 as that containing the female and the otheradult shrimp. While normally the hatching of the eggs of a gravid femalein the same tank with other adult shrimp is to be avoided, due to thecannibalistic tendencies of the adults, this problem is obviated in thepresent system by collecting hatched larvae during the hours thatimmediately follow the period of greatest likelihood of hatching. Thus,the substantial bulk of hatched larvae are removed from the enclosures 2soon after hatching, and mortality at the hands of the adult shrimp issubstantially precluded.

More specifically, collection of the hatched larvae, which are freeswimming, from each enclosure 2 is brought about, in part, by the watermovement or current created by the filtration of the enclosure, as wellas by additional lighting provided at preselected time periods. Thelatter lighting is in the form of a light source 27 placed adjacent theopening of the conduit 22 carrying water from the enclosure 2 into thefilter tank 3. This light illuminates the water leading to the conduitand is controlled, likewise, via a conventional timer 111 in the powerline 112 connecting the power source 103 to the light, so as to turn ondaily between preselected morning hours and, in particular, fromapproximately 2 a.m. to 7 a.m. The actual collecting of the larvae iscarried out by the placement of collection boxes 28 (FIGS. 3 and 4) inthe filtration tank 3 and the connection of these boxes to the conduit22 carrying water into the tank. These boxes have open tops 29 and twoopposing apertured sidewalls 31 and 32. The apertures are closed off bymesh 33 of sufficiently small mesh size to trap hatched larvae, whilepermitting passage of the medium 23. The collection boxes are typicallypositioned in their respective filtration tanks in the evening andremoved in the morning.

In general, the eggs of a gravid female are found to hatch between thehours of 12 a.m. to 2 a.m. The resultant hatched larvae, in turn, arephototrophic and, thus, are attracted to light. Thus, with the presentsystem, the bulk of the larvae hatched in each enclosure 2 each day willbe hatched between the aforesaid early morning hours and immediatelyupon hatching, or soon thereafter, these larvae will be subjected to thelight from the source 27, which is strongest in the area of theenclosure adjacent the conduit 22. The larvae will then be attracted tothe light and proceed to the aforesaid lighted area. The mild current ofthe medium 23, due to the filtration thereof, will thereupon furtherattract the larvae who will then follow the current and proceed into andthrough the conduit 22 and thereafter into the collection box 28, whichhad previously been connected thereto. The meshed sides of the box willthen prevent passthrough of the larvae, while permitting passthrough ofthe medium 23. As a result, the larvae will collect in the box forsubsequent transfer when the box is detached from the conduit.

With the present system, it has been found that a plurality of cycles ofmating, spawning and hatching of the adult shrimp can be carried outusing the common enclosures 2 without serious mortality and with a highyield of hatched larvae. Additionally, the use of the filtration tanks 3adjacent the enclosures 2 extends adult shrimp life by greatly reducingcontaminants, while it further aids in the larvae collection process.Collection of hatched larvae daily at preselected morning hours,moreover, ensures maximum collection and substantially nullifiesmortality due to cannibalism, thereby allowing hatching in the commonenclosures 2.

After collection of the hatched larvae, they are transferred from thelarvae collection boxes to the larvae tanks 4 where they are rearedthrough the larvae stage of development. As illustrated in FIGS. 2 and3, each of the larvae tanks 4 comprises an upper portion 41, shown ascylindrical, and a lower conical portion 42 whose bottom is truncated toform a flat, relatively broad bottom wall 42. Typically, the ratio ofthe width of the bottom wall 43 to the upper mouth of the conicalportion is about one to three.

Passing through an aperture 44 in the flat bottom wall 43 is a standpipe45 which extends upwardly into the conical portion to about one third ofits height. Outside the conical portion, the standpipe connects to adischarge line 46 which is controlled by a valve 47. Inside the conicalportion, the standpipe is surrounded by a cylindrical apertured sleeve48 which extends upward beyond the end of the standpipe 45 to the topportion 41 of the tank. The sleeve is further surrounded by a thin mesh,so that the apertured portions, therefore, are rendered incapable ofpassing larvae therethrough.

Situated above the top portion 41 of the larvae tank 4 is a conduitwhich is formed as a finely apertured bar 49. This conduit receives amedium to be supplied to the tank whose flow is controlled by a valve51.

The truncation of the lower conical portion 42 of the larvae tank 4decreases significantly the mortality of the larvae, since it preventsovercrowding of the larvae during molting and draining of the tank. Thelatter is accomplished by opening the valve 47 which causes the medium52 in the tank to pass through the apertures in the sleeve 48 and fromthere through the standpipe 45 until the tank level is at the level ofthe later, whereupon drainage ceases. During drainage, the larvae areprevented from being flushed out by the mesh on the sleeve 48 and,therefore, all gather in the lower conical portion 42. However, due tothe relatively broad extent of this tank portion, they are not congestedor overcrowded and, thus, are not significantly disturbed by thedrainage process. As a result, drainage of the tank can be carried outdaily, with the added benefit that medium 52 is maintained substantiallycontaminant free. This also significantly enhances larvae life.

Another benefit of this broad extent of the lower tank portion is thatit provides an area where molting larvae can descend and not beovercrowded. Again, this enhances larvae life.

After the tank has been drained, as aforesaid, the tank is filled byopening the valve 51 controlling the flow of medium 52 to the fill bar49. Typically, the salinity of the medium 52 is maintained at 14±0.5 pptand the medium is preheated to 28.5°±0.5° C. so that it is at the sametemperature as the medium already in the tank. Due to the plurality ofholes in the bar 49, the fill water enters the tank as a spray. Thisalso is beneficial to the larvae life, as the spray is sufficientlydispersive so as not to harm the larvae.

The larvae in the larvae tanks 4 are subjected to substantially the sameartificial light and temperature conditions as the adult shrimp in theenclosures 2. Thus, the larvae receive light for a 14 hour periodbetween 7 a.m. and 9 p.m. and, as above noted, the temperature of thewater in the tanks is maintained at 28.5° C. The larvae are alsoprovided with aeration via the air stones 12 placed in the larvae tanks.These stones are fed by the air lines 11 which couple to the airmanifold. The air stones aid in circulating the tank medium, whichpromotes larvae and food suspension.

As above noted, the system of the invention is further provided with anadditional set of tanks 6 which are used for Artemia (Brine shrimp)hatching. Artemia are employed as supplemental food for the larvae. EachArtemia tank 6 (FIGS. 5 and 6) has an upper cylindrical portion 61 and alower conical portion 62. The latter portion, at its apex 63, isprovided with an aperture 64 through which extends a conduit 65. Thisconduit is provided with a drain valve 66 whose operation permitsdraining of the tank and collection of the Artemia. In the interior ofthe tank, the conduit 65 extends upwardly and forms an annular containerwith the inner sidewall of the apex, which container acts as a debriscollector. Medium is provided to the tank via a conduit 66 alsocontrolled by a valve 67 and air is provided by air lines 11 extendinginto the tank and feeding air stones 68. Exterior to the tank andsurrounding the region thereof above the top of the conduit which endsabove the apex 63 of the bottom tank portion, is an annular light 69.

Collection of the Artemia is carried out by turning off the air beingsupplied to the tank via the line 11 and air stone 68 and turning on thelight 69. The tank is allowed to remain in this condition for a shortperiod of time, such as, for example, twenty minutes. During this time asubstantial amount of the debris which has accumulated in the tanksettles out and is collected in the annular container formed by the endof the conduit 65 and the inner wall of the lower bottom tank portionabove the apex 63. On the other hand, the Artemia are attracted to thelower tank portion above the top end of the conduit 65 and surrounded bythe light 69. Subsequent operation of the valve 66 to allow substantialdraining of the tank thus results in the Artemia being removed from thetank substantially free of accumulated debris, which, as above-noted,now lies below the top end of the conduit and between the latter and theinner tank wall.

During the aforesaid collection operation, in order to facilitategathering of the Artemia in the tank, via attraction by the light 69 itis preferable that the sides of the tank above the tank region in thevicinity of the light 69 be dark and further that a lid be placed on thetank. Additionally, the tank in the vicinity of the aforesaid tankregion should be clear, so as to permit the light from the source 69 toilluminate same and thereby attract the Artemia thereto.

As shown in the drawings, during the draining of the tank 6, the outputline is coupled to an Artemia collector 71 (FIGS. 7, 8 and 9) having anupper cylindrical portion 72 to which connect three sloping legs 73whose ends connect to an annular sleeve 74. A meshlike structure 75extends from the upper cylindrical portion 72 around the legs 73 and tothe sleeve forming a funnel like structure whose sidewalls are,preferably, at an angle greater than 50 degrees relative to thevertical. Three further support legs 76 extend straight downward fromthe upper cylinder portion 72 and act as support legs for standing thecollector. The upper cylinder portion is provided with an aperture 77through which extends an intake tube whose end 79 is tapered to guideincoming fluid around the cylinder wall. A further cup like member 81 isarranged below the sleeve 74.

When the medium with the Artemia leaves the Artemia tank, it is carriedto the intake 78 and coupled into the collector along the cylindricalwall. The mesh 75 permits passage of the medium, but inhibits Artemiapassage. As a result, the Artemia are conveyed by the mesh to the bottomsleeve 74 and into the cup 81, where they are collected.

It should be noted that the apparatus and method of the presentinvention as disclosed hereinabove are particularly adapted to therearing of shrimp of the Macrobrachium Rosenbergi species, although withsuitable modification, the system and apparatus can be adapted to otherspecies of shrimp as well as to other types of crustaceans.

In all cases, it is understood that the above-described arrangements aremerely illustrative of the many possible specific embodiments whichrepresent applications of the present invention. Numerous and variedother arrangements can readily be devised without departing from thespirit and scope of the invention.

What is claimed is:
 1. A method for rearing shrimp under controlledconditions through the larvae stage comprising:providing a commonenclosure having a medium therein and habitats disposed in the mediumfor male and female adult shrimp; maintaining the male and female adultshrimp in the common enclosure through a plurality of cycles of mating,spawning and hatching; filtering the medium in the common enclosure; andcollecting hatched larvae at predetermined times from the enclosuremedium as the medium is being conveyed during filtering.
 2. A method inaccordance with claim 1, wherein:the step of maintaining includespermitting free access of said adult shrimp to one another.
 3. A methodin accordance with claim 1, further including the step of:maintainingthe temperature of said medium at 28.5° C.; and providing light to saidenclosure for 14 hours per day.
 4. A method in accordance with claim 1,further including the step of:stocking said common enclosure with agreater number of female adult shrimp than male adult shrimp.
 5. Amethod in accordance with claim 1, wherein:the step of filteringincludes creating movement of said medium; and the step of collectingincludes inserting a collecting apparatus in the moving medium.
 6. Amethod in accordance with claim 5, wherein:the step of collectingincludes providing light adjacent where the collecting apparatus isinserted in said medium.
 7. Apparatus for rearing shrimp undercontrolled conditions through the larvae stage comprising:commonenclosure means for housing male and female adult shrimp during aplurality of cycles of mating, spawning and hatching, said enclosurehaving a medium therein; means for filtering the medium in saidenclosure, including a tank having a common wall with said enclosure,said common wall having an aperture, and means for moving said mediumfrom said enclosure through said aperture and into said tank; and meansfor collecting hatched larvae at predetermined times from the enclosuremedium as the medium is being conveyed during filtering through saidaperture and into said tank by said moving means.
 8. Apparatus inaccordance with claim 7, wherein:said enclosure includes habitats forsaid shrimp which open into a common area, thereby permitting freedom ofaccess of said shrimp to one another.
 9. Apparatus in accordance withclaim 7, wherein:said means for filtering filters said mediumcontinuously.
 10. Apparatus in accordance with claim 7 wherein:saidmeans for moving includes an air lift which conveys medium from thebottom of said tank into said common enclosure thereby raising the levelof medium in said enclosure relative to the level of medium in said tankand inducing flow of medium from said enclosure through said aperture.11. Apparatus in accordance with claim 10, wherein:said filtration meansincludes a bio-filter comprising a bed of coral rock impregnated withnitrification bacteria.
 12. Apparatus in accordance with claim 7,wherein:said collection means includes a light source for directinglight to the region of said medium adjacent said aperture.
 13. Apparatusin accordance with claim 11, wherein:said apparatus further includesmeans for maintaining said light source on during the early morninghours.
 14. Apparatus in accordance with claim 12 wherein:said means formaintaining maintains said light source on during the hours of 2 a.m. to7 a.m.
 15. Apparatus in accordance with claim 12, wherein:saidcollection means further includes: a collection box having mesh walls,and an intake means for receiving said medium as it passes from saidaperture into said tank.
 16. Apparatus in accordance with claim 15,wherein:said filtration means includes a conduit disposed within saidaperture; and said intake means includes means for detachably connectingto said conduit.